Conventionally, a paper feeding device is provided in, for example, a copying machine for feeding copy paper thereto. Among various types of such a feeding device, there is one wherein a rotatable paper tray which is rotatable to longitudinal and lateral feed positions is provided in order to feed the copy paper oriented longitudinally and laterally with respect to a feeding direction. In such a feeding device, the copy paper is stacked on a paper holding plate provided in the rotatable paper tray. The paper holding plate is lifted up and lowered by a lift-up mechanism, the lift-up mechanism being independent of the rotating operation of the rotatable paper tray and being driven by a motor. That is, a paper-feed end of the paper holding plate is lifted up and maintained in an inclined state by a lift plate coupled to the motor. The paper-feed end is lifted up to an upper-limit position where the copy paper is detected by an upper-limit detecting switch. Paper feeding then takes place according to the pick-up roller method.
However, in the conventional lift-up mechanism, a plurality of driving and transmission devices such as electro-magnetic clutches and gears are necessary in a driving mechanism which drives the lift plate, and a plurality of sensors are needed to control the driving mechanism, the sensors detecting the upper-limit position, a lower-limit position etc. of the copy paper. Moreover, a bulky decelerating device is necessary to decelerate the rotation speed of the motor in order to lift up the paper holding plate at a suitable speed. Consequently, a configuration thereof becomes more complicated and an increase in cost results.